Technical Abstract:
Routine piglet production procedures, for example teeth clipping, tail docking and castration, most likely cause pain and are under increasing scrutiny from the animal rights lobby. The objectives of this study were to assess the impact of 2 alternative methods of tail-docking on subsequent responses during a standard pain test – the formalin test. At three days of age, a total of 12 male and 12 female piglets from 4 litters were assigned to one of three treatments: Cold clipping (COLD) – tails docked using side-cutter pliers, Hot clipping (HOT) – tails docked using gas-heated cautery clippers, and Control (CON) – tails left undocked. For docking, approximately 5 cm of tail was removed. At 6 and 12 days of age, the piglets were subject to a formalin test, during which they were placed individually into a 1m × 1m × 1m solid-sided arena and a 100mL dose of 1% formalin was injected subcutaneously into the tip of the tail. Behaviour was measured continuously for 15 min following injection. Data were analyzed using repeated measures ANOVA in SAS. CON piglets carried out more tail wags than both docked treatments (19.6 vs. 0.8 – COLD, 2.2 – HOT, F=10.2, P<0.01). COLD piglets spent more time standing abnormally (13.3s vs. 0.3s – CON, 1.8s – HOT, F=5.6, P<0.05) and on day 12 tended to carry out more bouts of shaking (18.1 vs. 7.2 – CON, 1.8 – HOT, F=3.2, P<0.07) than other treatments. Across treatments, male piglets appeared to show greater pain responses than female piglets, with more bouts of abnormal standing (8.2 vs. 2.1, F=5.8, P<0.05) and shaking (11.6 vs. 4.3, F=4.7, P<0.05) and less time spent walking (122s vs. 198s, F=10.5, P<0.01). The results indicate that pain sensitivity appeared to be greatest in cold docked piglets and in male piglets. Docking using heated clippers may reduce pain during the time period measured, but long-term implications should be further investigated.